Tool alloy



Aug. 24, 1937. P. SCHWARZKOPF- 2,091,017

TOOL ALLOY.

Filed July 27, 1932 '(b) 4 r (c) Fig.1 30

increasin conten 1 v I i MOQC in K O 9 1o 18 20 2'! 3O dgcaeacsin o z a (s 90?: W 0, oznozc, 10% ca 102 3: t

.cons n (a) 81% w c,9% zc, 10% Co (1:) 72% W C, 18% mac, 10% c6 (e) sax-was, 27% M026, 10% co Maximurlof hardness appargntly at paint (a) composition 53 (c) 60 x Ya) I 1 :inttweass-iqngv content af M QC j decreaso I i i 86 l s ia nt 9 1o 18 2o 27 10% co (srgo we; 074M026 10% INVENTORY (AFBI we 9% Mb c, wzc F330 (b)=72% we, 18 M0 1; oz co y hwagho ()=63zwc, 272M0 6, 1'02; co W (d.)=54 zwr, 392M0 0, 10%co 1 ATTORNEYS.

apparently maxin'wum hardness at point (c) Patented Aug. 24, 1937 UNITED STATES PATENT OFFICE 2,001,017 V TOOL ALLOY Application July 27, 1932, Serial No. 625,042

Germany May 16, 1929 5 Claims.

This invention relates to a tool alloy and forms a continuation in part of my co-pending application Serial No. 452,132 filed May 13, 1930, for Production of hard metal alloys.

It is known in the production of highly eificient hard tools to employ carbides of tungsten or molybdenum prepared by sintering these components, pulverizing the product and pressing the powder in moulds which are subsequently highly heated. It is also known to add an auxiliary metal to the carbide of tungsten or molybdenum and then to sinter the whole in order to obtain tool materials which, besides being extremely hard, are tough as well.

The present invention consists in a tool alloy comprising a sintered product containing at least two carbides of tungsten, molybdenum, boron, silicon, titanium, zirconium, and vanadium which are obtained entirely in the form of mixed crystals by heating to a suflicient extent and the "usual addition amounting to about 3 to 20% of one or more metals such as nickel, cobalt and chromium. The mixed crystal is a homogeneous solid solution and consequently the product obtained is entirely different from the fritted products made by processes hitherto known.

Experiments have shown that the hardness of the mixed crystals comprised of the two carbides of the said metals is a function of the proportion in which the said carbides are present in the mixed crystal, and this function possesses a maximum. It is particularly advantageous to choose for use in the present invention crystals which lie in, or close to, this region of maximum hardness. A few tests are suflicient for this purpose. Taking for instance MOzCWzC and Co increasing th amount of MOzC, decreasing the amount of W2C, adding always 10% Co; then (1) 90% W20 and 0% M02C and 10% Co gives a Rockwell hardness of 55; (2) 81% W20 and 9% M020 and 10% 00 gives a Rockwell hardness of 62; (3) 72% W20 and 18% MOzC and 10% Co gives a Rockell hardness of 57.5; while (4) with 63% W2C and 27% MOzC and 10% Co the material is brittle. By these few tests it is possible to ascertain the hardest mixed crystal of the respective series. This is clearly shown in the diagrammatic drawing attached hereto.

The most favorable results have been obtained with mixed crystals of the system MOzCWC. The maximum hardness is obtained with an alloy containing 63% of tungsten carbide (WC), 27% of molybdenum carbide and 10% of cobalt; this alloy has a hardness of 69 Rockwell (diamond load=150 kg.). Satisfactory results are obtained with alloys within the composition range: 50 to 70% tungsten carbide (WC), 40 to 20% molybdenum carbide and 10% additional metal. When the additional metal is cobalt the hardness varies between 65 to 69 Rockwell for the composition range given. By way of comparison it may be stated that the Rockwell hardness of an alloy containing tungsten mono-carbide and 10% cobalt is 60, whilst that of an alloy of 90% molybdenum carbide and 10% cobalt is 51.

Any suitable known method may be used for the production of mixed crystals, more especially the carbides, e. g., of tungsten and molybdenum, can be suitably comminuted, mixed and heated up to 1,600 to 2,000 C. for about 1 to 2 hours until mixed crystals are formed, which latter are then mixed with the additional metal in powdered form, and the whole is moulded and sintered at a temperature of about 1,400 to 1,600" C. It is also possible to mix oxides of, for example, molybdenum and tungsten in finely or very finely divided form with additionsof suitably pulverized carbon, for example, lamp black, and to heat the mixture to a sufficient extent in an electric furnace, whereby, in the example given, a mixed crystal of tungsten carbide and molybdenum carbide is obtained. However, the mixed crystals may also be obtained by mixing very finely divided tungsten and molybdenum metal powder and carburizing the mixture by heat treatment in carbon-containing gases.

Whatever be the procedure in the formation of the hardest mixed crystal in any case a body is obtained which is superior in hardness to tungsten or molybdenum alone or tungsten carbide or molybdenum carbide alone.

An electric furnace can be employed for effecting the heating and sintering; the sintering may also be carried out by means of high frequency currents. In some cases particularly good results are obtained by carrying out the heating or sintering in a vacuum.

The carbides prepared according to the invention are extremely hard but require additions to increase the toughness of the alloy. As such additions use may be made of one or more of the auxiliary metals nickel, cobalt, chromium, either separately or in suitable admixture.

Tool alloys prepared according to the invention are, as a rule, not used for the production of the entire tool, but merely for the part of the tool which in practice is used directly for cutting, drilling, etc., and which is subject to wear.

In the accompanying drawing is shown diagrammatically: in Figure 1 a scale of hardness for certain alloys containing mixed crystals of MozGWzC and Co, and

Figure 2 a similar scale for compositions, containing WC, M020 and C0. Obviously the showing of Figs, 1 and 2 difier therein that in Fig. 1 (ii-tungsten carbide, and in Fig. 2 mono-tungsten carbide are used, beside (ii-molybdenum carbide and cobalt. In both figures the content of cobalt is held constant, while the ratios of tungsten carbide and molybdenum carbide, transformed into mixed crystals, are varied.

I claim:

1. Tool alloy consisting of about 50% to 70% tungsten mono-carbide (WC) and about 20% to 40% (ii-molybdenum carbide (MOzC) combined into mixed crystals of great hardness, and auxiliary metal taken from a group consisting of nickel, cobalt and iron, in substantial amounts, up to about 20%.

2. A sintered hard tool alloy consisting of about 0% to 9i% tungsten carbide, 3% to 40% molybdenum carbide, and 3% to 20% auxiliary metal, substantially taken from a group consisting of nickel, cobalt and iron.

3. A sintered hard tool alloy consisting of 60% to 94% di-tungsten carbide, 3% to 20% (ii-molybdenum carbide and 3% to 20% auxiliary metal, substantially taken from the iron group.

4. A sintered hard tool alloy consisting of about 40% to 82% tungsten mono-carbide, 15% to 40% di-molybdenum carbide and about 3% to 20% auxiliary metal, substantially taken from the iron group.

5. A sintered hard tool alloy consisting of about 40% to 94% tungsten carbide, 3% to 40% molybdenum carbide and 3% to 20% auxiliary metal, substantially taken from the iron group, said-carbides heated to form substantially mixed crystals within the range of greatest hardness of such mixed crystals.

PAUL SCHWARZKOPF. 

